Among scanning electron microscopes (hereinafter, referred to as SEM) that are known as one of the charged particle beam devices in a semiconductor manufacturing process, there are a critical dimension-SEM (hereinafter, referred to as CDSEM) that is used for measuring a dimension and a shape of a fine pattern and a defect review-SEM (hereinafter, referred to as DRSEM) that is used for clearly observing a fine pattern or for detecting a defect which occurs on the pattern to specify a cause of the occurrence.
FIG. 1 illustrates a structure of an electron optical system of a general SEM. Primary electron beam that is emitted from an electron gun are converged by a convergence lens, and scanning is two-dimensionally performed on a sample by using a deflection coil. An electron beam image can be obtained by capturing reflection/secondary electrons by a detector, the electrons being generated from the sample by the electron beam irradiation. In the CDSEM, the pattern dimension is measured from the secondary electron beam image by using a magnification of the scan image which is a ratio of a (constant) scan width on an imaging display with respect to a (variable) scan width of the electron beam on the sample. On the other hand, in the DRSEM, the defect is observed by using not only the secondary electron image but also a reflection electron beam image.
Meanwhile, as illustrated in FIG. 2, for example, Patent Document 1 also suggests an electron microscope equipped with an electron optical system which uses a plurality (2 or more) of reflection electron detectors which are arranged so as to be divided around an electron beam axis. By using such a detection device, reflection electrons which are reflected into multiple directions in a wider area can be detected as compared to a case of a structure with one detector by which only the reflection electrons can be obtained in single direction. And, signals obtained from the plurality of detectors are synthesized by using the same weight coefficient, so that a good-quality reflection electron image in arbitrary direction can be easily and rapidly displayed.